Manmade air pollution is a problem that increasing affects the health of mankind and the earth we live on. Factories are one of the largest air polluters. Gaseous byproducts generated by or as a part of manufacturing processes form a major portion of factory generated air pollution. Governments worldwide are taking a more aggressive role in legislating and regulating the amount of air pollution that factories may generate. In the United States, at least, each year seems to bring new and more restrictive government air pollution standards.
The semiconductor industry is but one of many industries trying to control air pollution. The venting of manufacturing process/reactant gases to the atmosphere is a major source of concern. Many semiconductor companies presently use central burn tubes and/or scrubbers to treat the gases from many reactors utilizing many processes (e.g., ammonia, hydrogen chloride, silane) before they are vented to the atmosphere. Many presently available burn tubes and scrubbers remove pollution particulates down to the micron size from the remaining exhaust gas(es). But burning these gases causes several unwanted side effects. Silicon dioxide is the result of silane burning in air--the resulting sand coats everything downstream from the burn tubes. Another disadvantage is that ammonium chloride is sometimes generated from the ammonia and hydrogen chloride reaction. More importantly, presently available central burn tubes and scrubbers do not control the problem of visible pluming from fume exhaust stacks. Central pollution removal systems are also expensive, costing millions of dollars to install, they must be able to treat and condition many different types of exhaust pollutants at the same time and they are difficult to modify to meet ever changing pollution standards.
All wafer fabs (world wide) are presently seeking an affordable solution to visible pluming from fume exhaust stacks. The prevention of these plumes will soon be a requirement of the U.S. Clear Air Act. Any wafer fab that uses Silane, HCL and Ammonia, in combination with water scrubbing systems will exhibit pluming. All CMOS processes use at least one combination of ammonia, hydrogen chloride, silane. A cost effective solution to the pluming problem is urgently needed.